Position measuring systems of this type are utilized in particular in connection with numerical controls for measuring the relative position of a tool in relation to a workpiece to be processed, as well as in coordinate measuring machines.
In incremental length and angle measuring systems, a grid-like, incremental measuring graduation is scanned with a scanning device and periodic analog signals are generated. Rectangular signals are formed from the periodic analog signals and are supplied to a forward/backward counter. The counter reading indicates the relative position of the objects to be measured. When the electrical supply fails, the counter reading and thus the knowledge of the relative position at that time is lost. In accordance with the state of the art it is necessary after a power loss to approach a bench mark, the absolute position of which is known. When passing this bench mark, the forward/backward counter is set to a pre-selected value and measuring must be started again.